Positive Power Over Pain

October 12, 2005|By WILLIAM HATHAWAY; Courant Staff Writer

If people are told it won't hurt, it often doesn't.

Demonstrating the power of the placebo, researchers found that volunteers who expected to feel mild pain did not report much discomfort after receiving a more painful stimulus, according to a study that appeared last month in the Proceedings of the National Academy of Sciences.

``Positive expectations produced an almost 28 percent decrease in pain ratings -- equal to a shot of morphine,'' says Dr. Tetsuo Koyama, a postdoctoral fellow at Wake Forest University Baptist Medical Center and lead author of the study.

The researchers taught 10 healthy volunteers to expect to feel three different levels of pain stimulus after a specific timed interval.

After a seven-second lapse, a low level of heat was applied to the subjects' skin; after 15 seconds a moderate level of heat; and after 30 seconds the highest level of heat.

Researchers then mixed up the intervals when they administered painful stimuli and discovered that the subjects' expectation of pain levels changed the level of discomfort they reported.

All 10 subjects reported high levels of pain when they expected the most painful stimulus.

However, the level of pain they reported after receiving the most painful stimulus dropped when they expected to receive a low or moderate level of pain.

Brain scans on the people in the experiments showed that there was an overlap in the brain regions active when they expected to feel pain and the regions active when they actually experienced pain.

``Pain is not solely the result of signals coming from an injured body region, but instead emerges from the interaction between these signals and cognitive information unique to every individual,'' says Robert Coghill, a neuroscientist at Wake Forest and an author of the study. ``The brain can powerfully shape pain, and we need to exploit its power.''